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Soft Starter Issues

Hi
I have a RTHD Screw R123 Chiller rated at 300RT (Trane). The soft starter is a Benshaw ( Model:RBX-1-S-180A-15C ). Its around 5 years old.
The chiller was initially tripping intermittently (the chiller MCB located within the chiller panel) and the starter did not show any specific fault. We did a megger test (by a competent electrical person) and found one the studs to be faulty. Replaced all studs because the job is rather messy and long (the chiller is on a performance contract and every day it is down, we lose "savings").

After the studs was changed, we still have intermittent trips - the fault showed by the starter is basically phase error and SCR shorting. I am suspect that that moisture could be the problem as the chiller can run for a day or more and trips without warning. Why I say moisture is that there are traces of rust in the board (I noticed this when the wiring etc was removed).

I find that the solution of simply replacing the starter is not the best unless we can pinpoint the issue but as usual all suppliers love to change things when there is a small (and big) problem

I intend to "dry" the circuits using CO cleaner (for electronic) after switching off all power supply - is this advisable?

Thanks.. yes its a R134A. Sorry for the mix up. I have another Centravac R123, 2 stage centrifugal at the same site .
But the error code was initially phase fault issue which was basically a false alarm as the rotation was fine and everything was checked before running. Than yesterday it show SCR shorting fault. The problem is that the chiller is able to start up, go on softloading and up to full load before tripping anywhere between 10 minutes to 7 days!

The SCR's of the Benshaw starter can be individually replaced if found to be faulty - As you are seeing random & intermittant faults related to/determined by phase measurement by the PCB I would be more concerned about your comment as underlined below.

1st question is why do you have moisture in the starter. You can remove the source of moisture but I suspect the damage may already be done

Originally Posted by HVAC_MY

After the studs was changed, we still have intermittent trips - the fault showed by the starter is basically phase error and SCR shorting. I am suspect that that moisture could be the problem as the chiller can run for a day or more and trips without warning. Why I say moisture is that there are traces of rust in the board (I noticed this when the wiring etc was removed).

I find that the solution of simply replacing the starter is not the best unless we can pinpoint the issue but as usual all suppliers love to change things when there is a small (and big) problem

I intend to "dry" the circuits using CO cleaner (for electronic) after switching off all power supply - is this advisable?

it is CO2.. but the the brand CRC calls it CO... . My bad ...again.. anxiousness in solving an expensive problem. I might resort to changing it to star-delta connection if possible because the chiller is on 24 hrs a day and is only shut down for maintenance works..but the client as usual have their preferences.

The SCR's of the Benshaw starter can be individually replaced if found to be faulty - As you are seeing random & intermittant faults related to/determined by phase measurement by the PCB I would be more concerned about your comment as underlined below.

1st question is why do you have moisture in the starter. You can remove the source of moisture but I suspect the damage may already be done

I have seen the CT's do this kind of stuff too, but it would typically go off on a ground fault alarm once in a while.

If a day goes by and you have learned nothing, I hope you got a lot of sleep.

The SCR's of the Benshaw starter can be individually replaced if found to be faulty - As you are seeing random & intermittant faults related to/determined by phase measurement by the PCB I would be more concerned about your comment as underlined below.

1st question is why do you have moisture in the starter. You can remove the source of moisture but I suspect the damage may already be done

This is what I have been telling Trane - why is there moisture in the board? - the answer ..it is normal and no effect... the usual run-around, aversion to fault!

This is the fault (by the digital display) I noticed as the chiller operated (again dismissed by the service people):

a) warning voltage high at L1-L2 - i checked with a portable power meter (Fluke 1735) and trended it to detect any high voltage - none at all
b) Rotation error - this was not true as rotation was correct and my compressor did not fall apart

c) trip and now SCR short

The unfortunate thing is that there are no competent person to actually diagnose the problem - it is just guesswork and everyone loves to just replaced the entire component!

I believe it is the PCB that is faulty but cant replace the board - they want to change the whole starter!

What kind of facility is the chiller in , is it used for a process chiller , is the atmosphere that the chiller is in the problem ? (moisture ,corrosion)
As far as fixing the problem, How many service calls are you willing to do before you could have just replaced the suspect part and be done with the issue ?

What kind of facility is the chiller in , is it used for a process chiller , is the atmosphere that the chiller is in the problem ? (moisture ,corrosion)
As far as fixing the problem, How many service calls are you willing to do before you could have just replaced the suspect part and be done with the issue ?

It is a 24 hour commercial cum data center building. The corrosion is basically due to condensation due to the cold surface - the chiller is located in the tropics so warm air is the norm here. Which is why I kept telling the supplier that that we need to do something - I am now considering coating panel surface with thermal insulation paint.

Well, we changed all 6 studs although only 1 was faulty - as a performance contractor we do not take shortcuts - the point of issue is that we were quite sure there was an issue with the starter but was told it was the studs or the MSB in the chiller panel. We actually told them to replace what is required or be ready with the replacement because one month of shutdown cost us around USD 25K in savings value - thus replacing faulty components is our target. Less service calls the better

I don't mind changing the starter but am contemplating of going for star delta since I dont need to start the chiller often....